What does this radiographic report of chest pa mean ... " there is crowding of the basal lung markings secondary to elevated diaphragm" thank you :)?

Lung base unexpanded: The diaphragm is a thin membrane like muscle which stretches downward to expand the lungs. when it relaxes it moves upward and lungs compress. sometimes one side of the diaphragm may remain elevated for various reasons. The basal portions of the lungs is the base, or bottom portion. When the diaphragm is high, the normal tissue crowds together and appears thicker. It is not necessarily abnormal